How Zapret's Hosts File Update Mechanism Bypasses Discord Blocking

Zapret bypasses Discord blocking by locally overriding DNS resolution through the Windows hosts file, forcing blocked domains to resolve to working IP addresses before traffic ever reaches ISP filters.

Zapret is an open-source Deep Packet Inspection (DPI) bypass tool that restores access to blocked services by combining WinDivert packet filtering with strategic hosts file manipulation. The hosts file update mechanism automatically downloads fresh IP mappings and injects them into the Windows system hosts file, effectively circumventing ISP-level blocks without requiring VPN infrastructure. This article examines exactly how this mechanism bypasses Discord blocking by analyzing the source code in the Flowseal/zapret-discord-youtube repository.

The Bypass Architecture: WinDivert and Local DNS Spoofing

Zapret's bypass relies on two coordinated components working at different layers of the network stack.

WinDivert operates at the packet level, intercepting all outbound TCP and UDP traffic—including DNS queries—before they leave the machine. This low-level driver, implemented via bin/WinDivert.dll and bin/WinDivert64.sys, ensures that traffic flows through Zapret's filtering logic regardless of application-specific behavior.

Hosts File Manipulation targets the DNS resolution phase. By default, Windows checks the hosts file located at C:\Windows\System32\drivers\etc\hosts before querying external DNS servers. When Zapret appends its domain-to-IP mappings to this file, the operating system resolves blocked domains locally, never exposing the DNS query to ISP-level filters. Because the IP address returned is valid and unblocked, WinDivert allows the subsequent TCP connection to proceed normally.

How the Hosts File Update Mechanism Works

The automated update mechanism resides in the service.bat script, specifically within the :hosts_update routine located around line 910.

The Download Process

When a user selects the update option from the service menu, the script executes a PowerShell command to fetch the latest hosts list from the upstream Zapret repository:

:hosts_update
    echo Updating hosts file ...
    set "HOSTS_URL=https://raw.githubusercontent.com/bol-van/zapret/master/hosts"
    set "TMP_HOSTS=%TEMP%\zapret_hosts.tmp"

    powershell -NoProfile -Command ^
        "Invoke-WebRequest -Uri %HOSTS_URL% -OutFile %TMP_HOSTS% -UseBasicParsing"

Some builds alternatively use bitsadmin for the download, but the retrieval target remains identical: the raw hosts file maintained in the bol-van/zapret repository.

The Merge Strategy

After downloading to a temporary location, the script performs a non-destructive merge that preserves existing user entries:

    if exist "%TMP_HOSTS%" (
        copy /Y "%TMP_HOSTS%" ".service\hosts" >nul
        type ".service\hosts" >> "C:\Windows\System32\drivers\etc\hosts"
        echo Hosts file updated.
    ) else (
        echo Failed to download hosts list.
    )
    pause
goto menu

The routine first caches the downloaded content in .service\hosts, then appends these entries to the system hosts file using the type command with the append redirection operator (>>). This concatenation method ensures that existing mappings remain intact while adding the latest Discord-specific IP addresses.

Discord-Specific Host Entries

The hosts list downloaded by the update mechanism contains static IP mappings for domains frequently blocked by DPI systems. For Discord, the entries typically include Cloudflare edge server addresses that remain accessible despite ISP restrictions.

Sample entries found in .service/hosts include:

# Zapret - Discord unblock entries

104.16.123.96  discord.com
104.16.124.96  discord.com
162.159.136.232 discord.com

When Windows resolves discord.com, it returns one of these IP addresses from the local hosts file rather than querying the ISP's DNS server. Consequently, the desktop client, web interface, and voice chat services connect directly to Discord's infrastructure through valid routes that bypass the block.

Running the Hosts Update

To activate the bypass, users execute the update through the interactive service manager:

:: Launch service.bat and select option 8
service.bat
:: Then enter: 8

The script displays confirmation messaging:

Downloading latest hosts list ...
Hosts file updated successfully.
Restart Discord (or refresh the web page) to apply the changes.

The restart requirement ensures that the Discord client flushes its DNS cache and establishes new connections using the updated IP mappings.

Summary

• Zapret's hosts file update mechanism downloads fresh IP mappings from https://raw.githubusercontent.com/bol-van/zapret/master/hosts via PowerShell or BITS.

• The routine in service.bat (around line 910) appends these entries to C:\Windows\System32\drivers\etc\hosts without overwriting existing custom mappings.

• By resolving Discord domains to working IPs locally, the system never sends DNS queries to ISP-controlled resolvers, effectively hiding the destination from DPI inspection.

• WinDivert complements this approach by ensuring that the subsequent TCP/UDP traffic to these IPs flows unimpeded through the packet filter.

• Users must restart Discord after updating to flush application-level DNS caches and establish connections using the new mappings.

Frequently Asked Questions

Is modifying the Windows hosts file safe?

Modifying the hosts file is a standard administrative procedure that carries minimal risk when performed by Zapret's automated script. The service.bat routine uses append operations (>>) to preserve existing entries, and the mappings only affect DNS resolution for specific blocked domains. Users can manually remove added entries by editing C:\Windows\System32\drivers\etc\hosts with administrator privileges if needed.

Why does Discord require a restart after updating the hosts file?

Discord maintains internal DNS caching and persistent TCP connections to its servers. When the hosts file updates with new IP mappings, existing connections continue using previously resolved addresses. Restarting the application forces Discord to perform fresh DNS lookups, which then return the updated IPs from the local hosts file, establishing connections through the unblocked routes.

What happens if the hosts file download fails?

If the PowerShell or BITS download fails—typically due to the update URL being blocked—the script outputs "Failed to download hosts list" and returns to the menu without modifying the system hosts file. Users can manually download the hosts list from an alternative source and place it in .service/hosts, then run the local merge portion of the script, or use a VPN temporarily to perform the update.

Does this mechanism unblock Discord voice chat or only text?

The hosts file update mechanism unblocks all Discord traffic, including voice chat, text channels, and the web interface. Since the bypass operates at the DNS resolution layer, it affects any protocol (TCP or UDP) that the Discord client initiates to the resolved IP addresses. WinDivert ensures that both signaling traffic and media streams pass through without DPI interference.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}